Cellular Phone Antenna with a Small Irradiation of the Human Head

A compensation method for reducing the irradiation of the head of a cellular phone user without degradation of the far field is analyzed. This method uses two radiators that are located in the near region of each other, and create a weak field area in this region. The impacts of the mutual coupling between closely located radiators on the input impedance, current distribution, and fields of the radiators are studied. It is shown that the structure of two closely spaced monopoles is equivalent to the superposition of two basic structures: a two-wire open-ended line, and a single monopole. The shape and dimensions of the dark spots and the irradiation-reduction factor are determined. To facilitate the field calculations in the near zone of the antennas, a method based on replacing a piecewise-homogenous medium by an equivalent homogenous medium is used. The calculations and the experimental results in the presence of the head qualitatively agreed.